Actually SE never lied. Also if you actually look on the pet bar (PS3/PS4 version) you will see there is still FOUR empty ability slots to be filled with potential new Egi abilities. So yeah the Egi could indeed get new abilities, maybe not for the release of HW but they could easily get them in the future.
Also you are not taking into consideration the work SE have to put into the game as a whole (what other MMO do you know of that has released an expansion as big as HW!) They need to prioritse the content for all players and rightly so. Trying to focus on implementing X number of new Egi, each one with unique play style would be a major ball ache for the developers and would mean something would have to be sacrificed in order to balance so many new Egi. Also you can't compare it to any other job as SMN is the only job in the FF franchise that utilizes a vast number of pets/summons.
SE have made the right call coz when you think about how the game works it's really the only viable option to give SMN's Egi of every Primal. If they were to do it your way we would probably only get 1-3 more new Egi tops.
Personally I would much rather have an Egi of every Primal that are glamours, than just a couple more unique Egi.